A hydraulic machine such as, for example, a hydraulic shovel and the like has, for example, a pressure sensor, pressure difference sensor, displacement sensor and the like disposed in the respective sections of the hydraulic fluid contained in a hydraulic drive unit for operating the machine to check the operating state of the hydraulic drive unit so that the pressure state and the like in the unit can be measured. The circumstance in which the pressure sensor and the like are disposed is the high pressure circumference in the hydraulic fluid contained in the unit. For example, the pressure sensor is usually arranged as an electric unit including a Wheatstone bridge circuit making use of strain gauges and the like. A hydraulic pressure as an object to be sensed is converted into an amount of electricity by the pressure sensor and sensed as an electric signal. The electric signal produced by the pressure sensor is derived from the high pressure interior of the unit to the outside thereof at an atmosphere pressure through a signal deriving line. A control unit is disposed outside the hydraulic drive unit to control the operation thereof and the thus sensed signal derived to the outside through the signal deriving line is input to the control unit and used for various controls effected thereafter as an information regarding the operating state.
In the above arrangement, a conventional typical arrangement for extracting the signal deriving line to the outside is such that, for example, a hole is bored in a portion of the metal vessel of the unit to cause the signal deriving line to pass therethrough and further the signal deriving line is fixed within the hole by the application of a hermetic seal structure to thereby seal hydraulic fluid as well as maintain electric insulation between the signal deriving line and the metal vessel. There has been conventionally a glass hermetic seal and plastic hermetic seal as such a hermetic seal.
The glass hermetic seal used in the conventional seal structure of the signal line deriving portion must be processed at a high temperature of about 1000.degree. C. in an N.sub.2 atmosphere by using a furnace. Therefore, a manufacturing cost is expensive as a whole. Further, a caution must be also paid to a coefficient of linear expansion and thus a metal material used as the core member of the signal line and the vessel wall being a base is limited. For example, Fe--Ni is used as the core member of the signal line and stainless steel having a large coefficient of expansion is used as the metal material of the vessel wall. As a result, the manufacturing cost is further increased. Further, brittleness is a problem due to the use of glass and thus the glass hermetic seal is difficult to be practically applied to construction machines and civil engineering machines.
Further, in the plastic hermetic seal, a problem arises in the force for bonding the hermetic seal to the metal material of the vessel wall serving as a base and there is a problem in that the plastic hermetic seal cannot be used at high pressure and lacks in durability.
Although the above example describes the structure by which an electric signal supplied from the electric unit disposed in the hydraulic drive unit at high pressure is derived to the outside of the unit at an atmospheric pressure through the signal deriving line, a similar problem may also arise in the case in which an electric signal is derived from an electric unit disposed in the interior of a vacuum vessel having a high degree of vacuum to the outside of the vessel at an atmospheric pressure.
Further, in the general consideration of the above problem, when there is a metal partition member for isolating the interior thereof from the outside such as, for example, a closed metal vessel and the regions on the opposite sides of the partition member must be isolated from each other and units disposed in the respective regions on the opposite sides must be bonded or communicated to each other through any rigid member, there must be provided a structure by which the member is caused to pass through a hole bored in the partition member and the hole is sealed. The seal structure is not limited to the case in which the pressures in the regions on the opposite sides of the partition member are greatly different but must be also applied to the case in which the physical or chemical conditions and the like in the regions on the opposite sides of the partition member are different (there exist different kinds of gases, liquids and the like).
Further, the member passing through the hole bored in the metal partition member is not limited to the afore-said signal deriving line but generally includes a member with necessary rigidity such as a conducting member for transferring an electric signal or electric power, pipe member for flowing various fluids, heat pipe for flowing a heat medium, optical fiber for transferring an optical signal, and the like. The aforesaid problem also arises when these members are caused to pass through the hole bored in the metal partition member and the hole is sealed.
Further, reference is cited here to two Japanese Unexamined Patent Application Nos. Sho 63-214429 and Sho 63-214430 as conventional technical literatures relating to the present invention. Although the technologies disclosed in these literatures are used to bond two members and do not propose a seal structure, they will be described below because these technologies can be understood as similar related technologies.
The technology disclosed in Japanese Unexamined Patent Application No. Sho 63-214429 relates to a structure for bonding a cylindrical member made of fiber-reinforced plastic to a metal mounting member. As shown in, for example, FIG. 1 to FIG. 3 of the literature, the structure is arranged such that an end of the cylindrical member is inserted into a hole bored in the mounting member, a reinforcing member is inserted into the stepped portion in the interior of the cylindrical member, and the portion around the inserting port of the hole of the mounting member is forcibly compressed by a punch pressure to cause plastic deformation (metal flow) to the inner surface of the hole of the mounting member so that the end of the cylindrical member is held by the plastically deformed portion and the reinforced member to thereby bond the cylindrical member to the mounting member. In the embodiment shown in FIG. 1, the metal flow is produced to the inner circumference portion in the vicinity of the opening at one end of the hole by applying a pressure by the punch. Further, the embodiment shown in FIG. 4 of the literature shows a bonding structure made by producing the metal flow to the inner circumferential portions in the vicinity of the openings on the opposite ends of the hole.
Further, the technology disclosed in Japanese Unexamined Patent Application No. Sho 63-214430 relates to a structure for bonding a fiber-reinforced plastic bar-shaped member to a metal mounting member and has substantially the same structure as the bonding structure making use of the metal flow which is described in the above literature (Japanese Unexamined Patent Application No. Sho 63-214429). For example, FIG. 10 of the literature shows the structure by which the metal flow is produced to the inner circumferential surface in the vicinity of the opening at one end of a hole and FIG. 11 of the literature shows the structure by which the metal flow is produced to the inner circumferential surfaces in the vicinity of the openings at the both ends of the hole.
The technologies disclosed in the above two literatures intend to bond the member made of the fiber-reinforced plastic to the metal mounting member by making use of the metal flow technology. From the view point of the sealing performance of a bonded portion, since the aforesaid cylindrical member or bar-shaped member made of the fiber-reinforced plastic is formed by impregnating resin into a hard fiber material such as carbon fiber, glass fiber or the like which is wound by a filament winding method or the like, it has an increased hardness as a whole and does not have desirable elastic plasticity, and thus the member cannot be effectively deformed and cannot exhibit a sufficient sealing performance. Therefore, the technologies disposed in the above two literatures simply intend to bond the fiber-reinforced resin member to the metal mounting member and do not intend to seal the portion between them. This fact is apparent from, for example, Japanese Unexamined Patent Application No. Sho 63-214429 wherein FIG. 7 shows that an O ring for seal is separately provided.
Further, when a problem is indicated from another point of view, although the bonding structure disclosed in Japanese Unexamined Patent Application No. Sho 63-214429 has a ring-shaped reinforcing material disposed in the interior of the cylindrical member of the fiber-reinforced plastic, the axial length thereof is substantially the same as the thickness of the metal mounting member. Therefore, even if the cylindrical member is compressed and bonded from the opposite sides thereof, when a bending stress is applied to the cylindrical member, the bending stress is applied about the circumference of the end of the reinforcing member as a fulcrum, and thus a problem arises in that creep is liable to be caused to the bonded portion and the reliability of the bonded portion is lowered. Further, in the bonding structure disclosed in Japanese Unexamined Patent Application No. Sho 63-214430, since the bar-shaped member made of the fiber-reinforced plastic has low rigidity at the portion thereof where the resin exists, a problem arises in that the vicinity of the compressed portion is locally and concentrically deformed, whereas since the member has high rigidity as a whole, a compressing force cannot be applied to the interior thereof.
An object of the present invention is to provide a seal structure for a member-passing-through hole bored or formed in a metal partition member by which the hole having a member passing therethrough can be sealed securely as well as stably for a long time with a very high pressure resistive performance, the seal structure further being simply arranged and made by a simple process at a low cost, in the structure for sealing the hole bored in the metal partition member, which isolates the inside region thereof from the outside, such as, for example, a pressure vessel, vacuum vessel and closed vessel for accommodating gas and liquid and which has a member such as, for example, a conductor or conductor pin for transferring an electric signal or electric power, other conductors, metal pipe member for flowing fluid, heat pipe for flowing a heat medium, optical fiber for transferring an optical signal, and the like each passing through the hole.